Receiving cell broadcast (cb) messages

ABSTRACT

A method for receiving cell broadcast messages is described. The method includes communicating with a first cell. The method also includes switching to communicating with a second cell. A cell broadcast channel is read after switching cells. The method further includes switching from a dedicated mode to a packet idle mode. The cell broadcast channel is reread once after switching from a dedicated mode to a packet idle mode. Other aspects, embodiments and features are also claimed and described.

RELATED APPLICATIONS AND PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.13/547,896, filed Jul. 12, 2012, for “RECEIVING CELL BROADCAST (CB)MESSAGES,” which is related to and claims priority from U.S. ProvisionalPatent Application Ser. No. 61/508,528, filed Jul. 15, 2011, for “CELLBROADCAST FOR DUAL SIM DEVICES,” and from U.S. Provisional PatentApplication Ser. No. 61/599,205, filed Feb. 15, 2012, for “PREDICTIVEDRX MODE FOR EFFICIENT RECEPTION OF THE CELL-BROADCAST SERVICE (CBS),”which are incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the present invention discussed in this applicationrelate generally to wireless communication systems. More specifically,embodiments of the present invention discussed in this applicationrelate to systems and methods for receiving cell broadcast (CB)messages.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, video, data and so on.These systems may be multiple-access systems capable of supportingsimultaneous communication of multiple mobile devices with one or morebase stations.

Mobile devices are typically battery operated. It is desirable tomaximize the battery life of mobile devices. One way to maximize batterylife is to shut off components within the mobile device during periodswhen those components are not needed/used. By shutting off thesecomponents, battery power is conserved without reducing the overall userexperience of the mobile device. One example of a component that may beshut off is a receiver.

When the mobile device is receiving Short Message Service (SMS) messagesusing the cell-broadcast service (CBS), the mobile device is typicallyon for the entire duration of the CBS to ensure that a desiredcell-broadcast (CB) message is not missed. In some configurations, anetwork may support a mode where the base station informs a mobiledevice of the scheduling of the cell-broadcast (CB) messages (referredto as CB discontinuous reception (CB-DRX)). See 3GPP TS 23.041,“Technical realization of Cell Broadcast Service,” and 3GPP TS 44.012,“Short Message Service Cell Broadcast (SMSCB) support on the mobileradio interface.” However, many networks do not support CB-DRX. Byreducing the power consumption of mobile devices while receiving CBmessages in networks that do not support CB-DRX, benefits may berealized.

As wireless communication systems have become more widely deployed, thenumber of radio access technologies (RATs) available has also increased.To increase the feasibility and mobility of a mobile device, the mobiledevice may be capable of communicating with more than one radio accesstechnology (RAT). Benefits may be realized by improved methods forreceiving cell broadcast (CB) messages while communicating with morethan one radio access technology (RAT).

SUMMARY OF SOME EXAMPLE EMBODIMENTS

A method for receiving cell broadcast messages is described. The methodincludes communicating with a first cell. The method also includesswitching to communicating with a second cell. After switching cells, acell broadcast channel is read. The method further includes switchingfrom a dedicated mode to a packet idle mode. The cell broadcast channelis reread once after switching from a dedicated mode to a packet idlemode.

The method may be performed by a wireless communication device. Thewireless communication device may use one or more subscriberidentification module cards. Cell broadcast scheduling message may notbe supported by the second cell. Reading a cell broadcast channel mayinclude searching the cell broadcast channel for a cell broadcastmessage.

An apparatus for receiving cell broadcast messages is also described.The apparatus includes a processor, memory in electronic communicationwith the processor and instructions stored in the memory. Theinstructions are executable by the processor to communicate with a firstcell. The instructions are also executable by the processor to switch tocommunicating with a second cell. The instructions are furtherexecutable by the processor to read a cell broadcast channel afterswitching cells. The instructions are also executable by the processorto switch from a dedicated mode to a packet idle mode. The instructionsare further executable by the processor to reread the cell broadcastchannel once after switching from a dedicated mode to a packet idlemode.

A method for receiving cell broadcast messages is described. A triggerto read a cell broadcast channel is received. It is determined that anetwork does not support cell broadcast scheduling messages. A rate atwhich the cell broadcast channel is read is reduced. The cell broadcastchannel is read at the reduced rate.

The method may be performed by a wireless communication device. Reducingthe rate at which the cell broadcast channel is read may include usingpseudo scheduling information. The pseudo scheduling information maygive a cell broadcast channel higher priority than a paging channel. Thepseudo scheduling information may be such that the wirelesscommunication device reads all cell broadcast message slots until aschedule map has expired.

It may be determined that all the desired messages have been read. Themethod may include discontinuing rereading the cell broadcast channel atthe reduced rate.

An apparatus for receiving cell broadcast messages is also described.The apparatus includes a processor, memory in electronic communicationwith the processor and instructions stored in the memory. Theinstructions are executable to receive a trigger to read a cellbroadcast channel. The instructions are also executable to determinethat a network does not support cell broadcast scheduling messages. Theinstructions are further executable to reduce a rate at which the cellbroadcast channel is read. The instructions are also executable toreread the cell broadcast channel at the reduced rate.

A method for receiving cell broadcast messages is described. A cellbroadcast channel is monitored. Slots where a desired message isexpected in the cell broadcast channel are calculated. The cellbroadcast channel is read only at the calculated slots.

The method may be performed by a wireless communication device. The cellbroadcast channel may be monitored for a continuous scan time to obtaina number of repetitions, a periodicity, and a last slot number. Therepetitions, the periodicity, and the last slot number may be used tocalculate slots where a desired message is expected. A cell broadcastcontinuous scan procedure may be performed if predictive scheduling hasfailed for any desired message.

Reading the cell broadcast channel only at the calculated slots may bepart of a cell broadcast predictive scan procedure. A cell broadcastcontinuous scan procedure may be performed if a refresh timer expiresduring the cell broadcast predictive scan procedure. The method may beperformed in a network that does not support a cell broadcast schedulingmechanism.

Monitoring a cell broadcast channel may include starting a continuousscan timer. Monitoring a cell broadcast channel may also include readingall cell broadcast message slots. Monitoring a cell broadcast channelmay further include determining whether a message ID and an updatenumber have changed since a previous cell broadcast channel slot.

If at least one of the message ID and update number have changed sincethe previous cell broadcast message slot, the number of repetitions forthe message ID may be incremented. When the continuous scan timerexpires, the message ID, a cell ID, the number of repetitions, a lastmessage slot number, and calculated periodicity may be stored. Themessage ID, the cell ID, the number of repetitions, the last messageslot number, and the calculated periodicity may be used to calculateslots where a desired message is expected.

An apparatus for receiving cell broadcast messages is described. Theapparatus includes a processor, memory in electronic communication withthe processor and instructions stored in the memory. The instructionsare executable by the processor to monitor a cell broadcast channel. Theinstructions are also executable by the processor to calculate messageslots where a desired message is expected in the cell broadcast channel.The instructions are further executable by the processor to read thecell broadcast channel only at the calculated message slots.

An apparatus configured for receiving cell broadcast messages isdescribed. The apparatus includes means for communicating with a firstcell. The apparatus also includes means for switching to communicatingwith a second cell. The apparatus further includes means for reading acell broadcast channel after switching cells. The apparatus alsoincludes means for switching from a dedicated mode to a packet idlemode. The apparatus further includes means for rereading the cellbroadcast channel once after switching from a dedicated mode to a packetidle mode.

A computer-program product for a receiving cell broadcast messages isalso described. The computer-program product includes a non-transitorycomputer-readable medium having instructions thereon. The instructionsinclude code for causing a wireless device to communicate with a firstcell. The instructions also include code for causing the wireless deviceto switch to communicating with a second cell. The instructions furtherinclude code for causing the wireless device to read a cell broadcastchannel after switching cells. The instructions also include code forcausing the wireless device to switch from a dedicated mode to a packetidle mode. The instructions further include code for causing thewireless device to reread the cell broadcast channel once afterswitching from a dedicated mode to a packet idle mode.

An apparatus configured for receiving cell broadcast messages isdescribed. The apparatus includes means for monitoring a cell broadcastchannel. The apparatus also includes means for calculating slots where adesired message is expected in the cell broadcast channel. The apparatusfurther includes means for reading the cell broadcast channel only atthe calculated slots.

A computer-program product for a receiving cell broadcast messages isalso described. The computer-program product includes a non-transitorycomputer-readable medium having instructions thereon. The instructionsinclude code for causing a wireless device to monitor a cell broadcastchannel. The instructions also include code for causing the wirelessdevice to calculate message slots where a desired message is expected inthe cell broadcast channel. The instructions further include code forcausing the wireless device to read the cell broadcast channel only atthe calculated message slots.

A wireless device configured for receiving cell broadcast messages isdescribed. The wireless device includes means for monitoring a cellbroadcast channel. The wireless device also includes means forcalculating message slots where a desired message is expected in thecell broadcast channel. The wireless device further includes means forreading the cell broadcast channel only at the calculated message slots.

A computer-program product for a receiving cell broadcast messages isalso described. The computer-program product includes a non-transitorycomputer-readable medium having instructions thereon. The instructionsinclude code for causing a wireless device to monitor a cell broadcastchannel. The instructions also include code for causing the wirelessdevice to calculate message slots where a desired message is expected inthe cell broadcast channel. The instructions further include code forcausing the wireless device to read the cell broadcast channel only atthe calculated message slots.

Other aspects, features and embodiments of the present invention willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific, exemplary embodiments of thepresent invention in conjunction with the accompanying figures. Whilefeatures of the present invention may be discussed relative to certainembodiments and figures below, all embodiments of the present inventioncan include one or more of the advantageous features discussed herein.In other words, while one or more embodiments may be discussed as havingcertain advantageous features, one or more of such features may also beused in accordance with the various embodiments of the inventiondiscussed herein. In similar fashion, while exemplary embodiments may bediscussed below as device, system, or method embodiments, it should beunderstood that such exemplary embodiments can be implemented in variousdevices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system with multiple wirelessdevices according to some embodiments of the present invention;

FIG. 2 is a block diagram illustrating cell broadcast channel (CBCH)mapping to SDCCH/4 according to some embodiments of the presentinvention;

FIG. 3 is a block diagram illustrating cell broadcast channel (CBCH)mapping to SDCCH/8 according to some embodiments of the presentinvention;

FIG. 4 is a block diagram illustrating the structure of a cell broadcast(CB) message according to some embodiments of the present invention;

FIG. 5 is a flow diagram of a method for optimizing the reception ofcell broadcast (CB) messages according to some embodiments of thepresent invention;

FIG. 6 is a flow diagram of another method for optimizing the receptionof cell broadcast (CB) messages according to some embodiments of thepresent invention;

FIG. 7 illustrates data flows between a wireless communication deviceand a network, where pseudo scheduling is implemented after determiningthat the network has not sent a cell broadcast scheduling messageaccording to some embodiments of the present invention;

FIG. 8 illustrates data flows between a wireless communication deviceand the network, where pseudo scheduling is renewed periodicallyaccording to some embodiments of the present invention;

FIG. 9 illustrates data flows on a wireless communication device thatimplements pseudo scheduling according to some embodiments of thepresent invention;

FIG. 10 also illustrates data flows on a wireless communication devicethat implements pseudo scheduling according to some embodiments of thepresent invention;

FIG. 11 is a flow diagram of a method for receiving cell broadcast (CB)messages according to some embodiments of the present invention;

FIG. 12 is a flow diagram of a method for receiving cell broadcast (CB)messages using a cell broadcast (CB) continuous scan procedure accordingto some embodiments of the present invention;

FIG. 13 is flow diagram of a method for performing a predictive cellbroadcast discontinuous reception (CB-DRX) scan procedure according tosome embodiments of the present invention; and

FIG. 14 illustrates certain components that may be included within awireless communication device according to some embodiments of thepresent invention.

DETAILED DESCRIPTION OF ALTERNATIVE & EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system 100 with multiple wirelessdevices. Wireless communication systems 100 are widely deployed toprovide various types of communication content such as voice, data, andso on. A wireless device may be a base station 102 or a wirelesscommunication device 104.

A base station 102 can communicate with one or more wirelesscommunication devices 104. A base station 102 may also be referred to asand may include some or all of the functionality of, an access point, abroadcast transmitter, a NodeB, an evolved NodeB, etc. The term “basestation” will be used herein. Each base station 102 providescommunication coverage for a particular geographic area. A base station102 may provide communication coverage for one or more wirelesscommunication devices 104. The term “cell” can refer to a base station102 and/or its coverage area, depending on the context in which the termis used.

Communications in a wireless communication system 100 (e.g., amultiple-access system) may be achieved through transmissions over awireless link. Such a communication link may be established via asingle-input and single-output (SISO), multiple-input and single-output(MISO), or a multiple-input and multiple-output (MIMO) system. A MIMOsystem includes transmitter(s) and receiver(s) equipped, respectively,with multiple (N_(T)) transmit antennas and multiple (N_(R)) receiveantennas for data transmission. SISO and MISO systems are particularinstances of a MIMO system. The MIMO system can provide improvedperformance (e.g., higher throughput, greater capacity or improvedreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

The wireless communication system 100 may utilize MIMO. A MIMO systemmay support both time division duplex (TDD) and frequency divisionduplex (FDD) systems. In a TDD system, uplink and downlink transmissionsare on the same frequency region so that the reciprocity principleallows the estimation of the downlink channel from the uplink channel.This enables a transmitting wireless device to extract transmitbeamforming gain from communications received by the transmittingwireless device.

The wireless communication system 100 may be a multiple-access systemcapable of supporting communication with multiple wireless communicationdevices 104 by sharing the available system resources (e.g., bandwidthand transmit power). Examples of such multiple-access systems includecode division multiple access (CDMA) systems, wideband code divisionmultiple access (W-CDMA) systems, time division multiple access (TDMA)systems, frequency division multiple access (FDMA) systems, orthogonalfrequency division multiple access (OFDMA) systems, single-carrierfrequency division multiple access (SC-FDMA) systems, 3^(rd) GenerationPartnership Project (3GPP) Long Term Evolution (LTE) systems, andspatial division multiple access (SDMA) systems.

The terms “networks” and “systems” are often used interchangeably. ACDMA network may implement a radio technology such as UniversalTerrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes W-CDMA andLow Chip Rate (LCR) while cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asGlobal System for Mobile Communications (GSM). An OFDMA network mayimplement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11,IEEE 802.16, IEEE 802.20, Flash-OFDMA, etc. UTRA, E-UTRA, and GSM arepart of Universal Mobile Telecommunication System (UMTS). Long TermEvolution (LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA,GSM, UMTS and Long Term Evolution (LTE) are described in documents froman organization named “3rd Generation Partnership Project” (3GPP).cdma2000 is described in documents from an organization named “3rdGeneration Partnership Project 2” (3GPP2).

A wireless communication device 104 may also be referred to as and mayinclude some or all of the functionality of, a terminal, an accessterminal, a user equipment (UE), a subscriber unit, a station, etc. Awireless communication device 104 may be a cellular phone, a personaldigital assistant (PDA), a wireless device, a wireless modem, a handhelddevice, a laptop computer, etc.

A wireless communication device 104 may communicate with zero, one, ormultiple base stations 102 on the downlink 106 a-b and/or uplink 108 a-bat any given moment. The downlink 106 (or forward link) refers to thecommunication link from a base station 102 to a wireless communicationdevice 104, and the uplink 108 (or reverse link) refers to thecommunication link from a wireless communication device 104 to a basestation 102.

In embodiments of the present invention, a wireless communication device104 may be capable of communicating with a first base station 102 a aspart of a first radio access technology (RAT) 112 a and a second basestation 102 b as part of a second radio access technology (RAT) 112 b.Examples of radio access technologies (RATs) 112 include Global Systemfor Mobile Communications (GSM), 1x (also known as cdma2000 1x), highdata rate (HDR), W-CDMA, and Long Term Evolution (LTE). The wirelesscommunication device 104 may use dual SIM dual standby (DSDS) tocommunicate with two radio access technologies (RATs) 112. In dual SIMdual standby (DSDS), a wireless communication device 104 has twosubscriber identification module (SIM) cards. However, the wirelesscommunication device 104 is not required to use SIM cards. Thus, awireless communication device 104 that uses dual SIM dual standby (DSDS)may be any wireless communication device 104 that is capable ofcommunicating using more than one radio access technology (RAT) 112.Dual SIM dual standby (DSDS) is a popular feature in China, India, SouthEast Asia, Latin America, and other markets.

The wireless communication device 104 may communicate with differentcombinations of radio access technologies (RATs) 112. For example, awireless communication device 104 may be capable of communicating withboth a Global System for Mobile Communications (GSM) radio accesstechnology (RAT) 112 and a 1x radio access technology (RAT) 112; aGlobal System for Mobile Communications (GSM) radio access technology(RAT) 112 and a high data rate (HDR) radio access technology (RAT) 112;or a 1x radio access technology (RAT) 112 and a high data rate (HDR)radio access technology (RAT) 112.

To be competitive in markets utilizing dual SIM dual standby (DSDS), awireless communication device 104 may need to have optimal powerconsumption and lower hardware cost. For example, a wirelesscommunication device 104 that has higher power consumption and a dualreceiver may be unable to compete in a dual SIM dual standby (DSDS)market. Thus, reducing hardware cost and power consumption of a dual SIMdual standby (DSDS) wireless communication device 104 is desirable.

When a wireless communication device 104 is reading the cell broadcastchannel (CBCH) and the paging channel (PCH) while in dual SIM mode, ahigher rate of collisions may occur due to the shorter paging schedule.This higher rate of collisions may lead to, in one implementation, anincrease in the number of cell broadcast (CB) messages that are missedby the wireless communication device 104. Cell broadcast (CB) messagesmay also be referred to as cell broadcast short message service (CB-SMS)messages). In another implementation, the higher rate of collisions maylead to an increase in the number of paging channel (PCH) messages thatare missed by the wireless communication device 104. Thus, increasingthe ability of the wireless communication device 104 to minimize thenumber of cell broadcast (CB) messages that are missed or dropped ishighly desirable.

To optimize reception of cell broadcast (CB) messages, a wirelesscommunication device 104 may reduce the cell broadcast channel (CBCH)reading frequency 133. This may be done by a cell broadcast (CB) task inthe wireless communication device 104. The cell broadcast (CB) task inthe wireless communication device 104 may know how many pages areincluded in a cell broadcast (CB) message. The cell broadcast (CB) taskcan use a pseudo scheduling approach if a network does not use cellbroadcast scheduling.

The wireless communication device 104 may also raise the priority 135for a cell broadcast channel (CBCH) read if the cell broadcast channel(CBCH) collides with the paging channel (PCH). The GERAN logical layer(L1) in the wireless communication device 104 may be the best place todo this. In a dual SIM wireless communication device 104, activity thatrequires the use of the radio (e.g., read the broadcast control channel(BCCH), read the paging channel (PCH), a voice call, a data call) isgiven a priority 135. When two radio access technology (RAT) controllers110 a-b require the use of the radio at the same time, the priority 135may be used to determine which radio access technology (RAT) controller110 a-b gets to use the radio. Normally, reading the paging channel(PCH) gets higher priority but with pseudo scheduling, the cellbroadcast channel (CBCH) is given a higher priority, since cellbroadcast channel (CBCH) reading is done at a much lower rate (i.e.,once every 30 seconds), while paging channel (PCH) reading happens muchmore frequently. Combining the use of a raised priority 135 for cellbroadcast channel (CBCH) reading and reducing the cell broadcast channel(CBCH) reading frequency 133 may minimize the number of missed pagingchannel (PCH) blocks while also minimizing additional power consumptiondue to the reading of the cell broadcast channel (CBCH).

In one configuration, the wireless communication device 104 may performcell broadcast channel (CBCH) reading only upon first camping on a cell.This can reduce the number of missed paging channel (PCH) blocks whilealso minimizing power consumption due to the reading of the cellbroadcast channel (CBCH). This may be a configurable option, since itmay not suitable for all markets or other network environments.

If the wireless communication network 100 supports the use of the cellbroadcast channel (CBCH), the base station 102 may broadcast a cellbroadcast (CB) page every 1.88 seconds (8*51 multiframes) on the cellbroadcast channel (CBCH). If a wireless communication device 104supports simultaneous standby for two or more subscriptions, there maybe a high probability that a collision occurs between a cell broadcast(CB) reception by one subscription and the page read of anothersubscription. Thus, there is a tradeoff between paging channel (PCH)reads and cell broadcast channel (CBCH) reads. For a subscription whosepaging channel (PCH) read is missed, the subscription may go out ofservice due to the collisions. There is also a possibility that noreading of the cell broadcast channel (CBCH) may occur if twosubscriptions camp on the same network.

In embodiments of the present invention, the wireless communicationnetwork 100 may support discontinuous reception (DRX) of cell broadcast(CB) messages. In cell broadcast (CB) discontinuous reception (CB-DRX),the base station 102 may signal to the wireless communication device 104which cell broadcast (CB) message will be broadcast and when bybroadcasting a cell broadcast (CB) schedule message. CB-DRX thus allowsthe wireless communication device 104 to power down a receiver on thewireless communication device 104 during periods when the base station102 is not broadcasting a cell broadcast (CB) message that is desired bythe wireless communication device 104. However, many networks do notsupport CB-DRX mode. If a network does not support CB-DRX mode, thewireless communication device 104 may have to decode every cellbroadcast channel (CBCH) slot at a rate of 8*51 multiframes to obtainthe desired message, resulting in increased power consumption by thewireless communication device 104.

To reduce the power consumption by a wireless communication device 104in a network that does not support CB-DRX mode, the wirelesscommunication device 104 may include a cell broadcast (CB) predictivescan module 114. The cell broadcast (CB) predictive scan module 114 mayallow the wireless communication device 104 to predict when the basestation 102 is likely to broadcast a desired message, thereby allowingthe wireless communication device 104 to power down during periods whenthe desired message is not broadcast, thereby conserving battery power.Use of the cell broadcast (CB) predictive scan module 114 also minimizescollisions between page reception and cell broadcast (CB) reception inmulti-subscription wireless communication devices 104.

The cell broadcast (CB) predictive scan module 114 may include a refreshtimer 116. When the cell broadcast (CB) predictive scan module enters apredictive CB-DRX mode, the wireless communication device 104 may startthe refresh timer 116. When the refresh timer 116 expires, the wirelesscommunication device 104 may exit predictive CB-DRX mode to refresh thesettings for the cell broadcast (CB) predictive scan module 114.Periodically refreshing the settings for the cell broadcast (CB)predictive scan module 114 may reduce the possibility of missed desiredmessages when the base station 102 changes the pattern of broadcastingthe desired messages.

The cell broadcast (CB) predictive scan module 114 may also include acontinuous scan timer 118. Prior to entering predictive CB-DRX mode, thewireless communication device 104 may perform a continuous scan of thecell broadcast (CB) messages to determine which cell broadcast (CB)messages are broadcast by the network and how these cell broadcast (CB)messages are repeated. During the continuous scan, the wirelesscommunication device 104 may determine the number of repetitions 120 fora desired message, the message ID 122, the cell ID 124, and theperiodicity 128. The continuous scan may be performed until thecontinuous scan timer 118 expires. Once the continuous scan timer 118expires, the cell broadcast (CB) predictive scan module 114 may alsodetermine the last slot number 126 the desired message or messages werereceived in. During the continuous scan, whenever the cell broadcast(CB) predictive scan module 114 detects a new message ID 122, therespective count parameter may be incremented. There may be one counterfor each message ID 122 to count how many times the message ID 122 hasbeen repeated and in which cell broadcast (CB) slots the messagecorresponding to the message ID 122 was sent in. The continuous scan mayoccur over a window of duration MxN slots, where M is the number ofmessages that will have different message IDs 122 and N is multiples of49 slots. A value of 49 has been selected for N because this is themaximum duration of schedule information provided by the network if thenetwork supports CB-DRX mode. As an example, if the number of messageswhich will have different message IDs 122 is 3 (i.e., three differentdesired messages are watched by the cell broadcast (CB) predictive scanmodule 114) and a multiple of 3*49 slots is used, the number of slotsfor the continuous scan timer 118 may be 3*3*49=441. In other words, 441continuous slots may be examined during continuous scan mode.

The cell broadcast (CB) predictive scan module 114 may determine thenumber of consecutive repetitions 120 of the same message ID 122. Thenumber of repetitions 120, the message ID 122, the cell ID 124, theperiodicity 128, and the last slot number 126 may be settings for apredictive CB-DRX mode scan procedure in embodiments of the presentinvention. Thus, the cell broadcast (CB) predictive scan module 114 mayuse the number of repetitions 120, the message ID 122, the cell ID 124,the periodicity 128, and the last slot number 126 to predict when thebase station 102 is likely to broadcast a desired message. In otherwords, when in predictive CB-DRX mode, the wireless communication device104 may only read the slots where a desired message is predicted to bebroadcast.

The cell broadcast (CB) predictive scan module 114 may predict the validdata message slots and adapt the wireless communication device 104 toread the cell broadcast channel (CBCH) during those valid data messageslots. The adaptive approach may fall onto an integer multiple of an8*51-multiframe. The cell broadcast (CB) predictive scan module 114 mayreduce the power consumption of the wireless communication device 104significantly as the wireless communication device 104 tracks the cellbroadcast (CB) messages broadcast by the network. Recent studies haveindicated that cell broadcast (CB) messages do not change frequently(e.g., the message ID 122 and update number 129 are fairly constant).

Every cell broadcast (CB) message is given a message sequence number. Acombination of the message ID 122 and the message sequence number makeseach message unique. If the message sequence number has changed, thatmeans that the message contents have changed and the wirelesscommunication device 104 should reread this message. The update number129 is a part of the serial number. The update number 129 may beincremented by the network if an old message needs to be updated. Thewireless communication device 104 may replace the old message with thenew message in such cases.

The use of the cell broadcast (CB) predictive scan module 114 may reducethe probability of collisions in multi-SIM devices when one subscriptionreads the cell broadcast channel (CBCH) and another subscription readsthe paging channel (PCH). However, if the network updates the cellbroadcast (CB) messages frequently, very little power savings may beachieved. Furthermore, if the periodicity 128 is not constant, verylittle power savings may be achieved. In this case, the cell broadcast(CB) predictive scan module 114 may return to continuous scan modefrequently. Nevertheless, any use of a predictive CB-DRX mode scanprocedure may provide a reduction in power consumption compared tonon-DRX mode.

FIG. 2 is a block diagram illustrating cell broadcast channel (CBCH)mapping 232 to SDCCH/4. There are two cell broadcast channels (CBCH)defined in the specification: the cell broadcast channel (CBCH) basicand the cell broadcast channel (CBCH) extended. Both the cell broadcastchannel (CBCH) basic and the cell broadcast channel (CBCH) extendedoccupy the same frames within a 51-multiframe 230. However, the cellbroadcast channel (CBCH) basic uses 51-multiframes 230 with TC=0, 1, 2and 3 while the cell broadcast channel (CBCH) extended uses51-multiframes 230 with TC=4, 5, 6 and 7.

TC is a modulo 8 counter that counts the number of 51-multiframes 230.TC=mod(int(FN/51), 8), where FN is the Frame Number. For example, TC=0for frame numbers 0-50, TC=1 for frame numbers 51-101, TC=2 for framenumbers 102-152, TC=3 for frame numbers 153-203, TC=4 for frame numbers204-254, TC=5 for frame numbers 255-305, TC=6 for frame numbers 306-356and TC=7 for frame numbers 357-407. Then it repeats; thus TC=0 for framenumbers 408-458. One TC cycle thus has 408 frames. Each cell broadcast(CB) message may be sent over one or more TC cycles.

All wireless communication devices 104 are expected to read the cellbroadcast channel (CBCH) basic (this is mandatory for GSM capabledevices). However, the reading of the cell broadcast channel (CBCH)extended is optional. Both the cell broadcast channel (CBCH) basic andthe cell broadcast channel (CBCH) extended are optional for the network.If the network supports the cell broadcast channel (CBCH), the networkmay generally support cell broadcast channel (CBCH) basic becausewireless communication devices 104 are only mandated to support thischannel. The network may optionally also support cell broadcast channel(CBCH) extended but the network cannot rely on wireless communicationdevices 104 to read the cell broadcast channel (CBCH) extended.

The two cell broadcast channels (CBCHs) are considered as parallelchannels. The network must broadcast a complete cell broadcast (CB)message on one cell broadcast channel (CBCH). The network cannot sendpart of a cell broadcast (CB) message on one cell broadcast channel(CBCH) and part of the cell broadcast (CB) message on another cellbroadcast channel (CBCH). The network may repeat the same message onboth cell broadcast channels (CBCHs) or send different messages on eachcell broadcast channel (CBCH).

A cell broadcast channel (CBCH) may be mapped to a physical channelusing two possible formats: SDCCH/8 and SDCCH/4, where SDCCH refers tothe stand-alone dedicated control channel. SDCCH/8 is discussed inadditional detail below in relation to FIG. 3. The SDCCH/4 mappingformat may be used when the network deploys a combined common controlchannel (CCCH)+SDCCH. The SDCCH/8 mapping format is used with anon-combined common control channel (CCCH).

When the cell broadcast channel (CBCH) is mapped to SDCCH/4, the networkis using combined CCCH+SDCCH in a cell. Hence, the cell broadcastchannel (CBCH) uses the same frequency and timeslot as the broadcastcontrol channel (BCCH). In this case, the cell broadcast channel (CBCH)does not collide with the broadcast control channel (BCCH) or the pagingchannel (PCH) blocks. The use of SDCCH/4 mapping is most likely to beused in rural or sparsely populated areas, as there are only up to threepaging opportunities within one 51-multiframe 230. This is because halfof the 51-multiframes 230 are used for dedicated connections signalingpurposes only and not speech. Signaling connections are needed forregistration, periodic updates, short message service (SMS), etc. Thecell broadcast channel (CBCH) is thus mapped to multiframes 32, 33, 34and 35 within a 51-multiframe 230. This is fixed by the specification.

FIG. 3 is a block diagram illustrating cell broadcast channel (CBCH)mapping to SDCCH/8. In this case, the cell broadcast channel (CBCH) ismapped to a different physical channel than the broadcast controlchannel (BCCH) or the common control channel (CCCH). The specificationallows the cell broadcast channel (CBCH) to be mapped to any frequency,but it is far more optimal to map the cell broadcast channel (CBCH) to aphysical channel on the broadcast control channel (BCCH) carrier butusing a different timeslot.

There are two different 51-multiframes 330 a-b shown in FIG. 3. Onemultiframe 330 a is dedicated for all common control channels (broadcastcontrol channel (BCCH), paging channel (PCH), access grant channel(AGCH), random access channel (RACH), etc., except the cell broadcastchannel (CBCH)). The broadcast control channel (BCCH) is always ontimeslot 0, while the paging channel (PCH), access grant channel (AGCH)and random access channel (RACH) can be on timeslot 0 or both 0 and 2 or0, 2 and 4 or 0, 2, 4 and 6. The other 51-multiframe 330 b has fourradio frames on one timeslot only set aside for the cell broadcastchannel (CBCH).

FIG. 4 is a block diagram illustrating the structure of a cell broadcast(CB) message 436. As discussed above, a cell broadcast (CB) message 436may also be referred to as a cell broadcast short message service(CB-SMS) message. Each cell broadcast (CB) message 436 may be up to 1230octets long. The cell broadcast (CB) message 436 may be split into up to15 pages, each page having a maximum size of 82 octets of user data.Each page of the cell broadcast (CB) message 436 may then be sent infour consecutive radio blocks on the cell broadcast channel (CBCH).

Each page of the cell broadcast (CB) message 436 includes a page header.The page header includes a serial number, a message identifier, a datacoding scheme, the total number of pages and the page number followed bya cell broadcast (CB) short message service (SMS) segment. Each page maybe split up into up to four radio blocks and each radio block includesthe block header (which indicates the block number and whether it is thelast block of the page). Because the first radio block always includesthe page header, it is necessary for the wireless communication device104 to read this block to determine if the remaining three radio blocksshould be read or not.

The ability to read the cell broadcast channel (CBCH) for onesubscription while maintaining sufficient paging reception performanceon the other subscription may depend on the network configuration. Cellbroadcast (CB) reception may be obtained for G+G and G+W configurations.It may be assumed that the relative alignment of the two GERAN cells(i.e., the cell of the first subscription and the cell of the secondsubscription) does not change significantly over time. The possibilityof a collision of the paging channel (PCH) for one subscription and thecell broadcast channel (CBCH) for the other subscription may depend onthe alignment of the two 51-multiframes 330 and the paging multiframe. Ashorter paging discontinuous reception (DRX) cycle equals a highcollision probability. The probability of a paging channel (PCH)collision with a cell broadcast channel (CBCH) depends on devicearchitecture but can be on the order of 20%.

A collision of a paging channel (PCH) read with a cell broadcast channel(CBCH) read may be a persistent occurrence or an intermittentoccurrence, depending on the paging cycle used in the cell. Table 1below lists whether a collision will occur for different paging cyclesused in a cell. A collision is considered to have occurred when all fourconsecutive cell broadcast (CB) message 436 blocks (also referred to asa cell broadcast (CB) message slot) can not be read. Therefore, acollision will happen when the number of 51-multiframes 330 between twoconsecutive monitored paging multiframes is less than five.

TABLE 1 Paging cycle Collision 2 Yes 3 Yes 4 Yes 5 No 6 No 7 No 8 No 9No

For cases where the cell broadcast channel (CBCH) reading collides withthe paging channel (PCH) reading (and thus the cell broadcast channel(CBCH) could not be read), some work-around mechanism may be necessary.One workaround mechanism is to skip the paging channel (PCH) reading andallow the cell broadcast channel (CBCH) reading to take place. Thedrawback of this approach is that it could lead to missedmobile-terminated calls. For some situations, this may be the onlyoption. The paging reception performance may be improved by lowering therate at which the cell broadcast channel (CBCH) refresh is performed.This is discussed in additional detail below in relation to FIG. 7 andFIG. 8.

Another workaround mechanism is to read different blocks of the cellbroadcast page during different TC cycles, when possible. Thedisadvantage of this approach is that if the network modifies the cellbroadcast (CB) message 436, the wireless communication device 104 mayend up combining user text from different instances of a message or fromdifferent messages (even worse). Therefore, this workaround is notsuitable for markets where cell broadcast (CB) messages 436 are likelyto change (and is thus not suitable for the present systems andmethods).

Table 2 below illustrates the number of consecutive paging blocks thatmay be missed for different paging cycles.

TABLE 2 Number of consecutive paging Paging blocks cycle missed Comments2 2 With this paging cycle, two of the four blocks will always collidewith CBCH reads. There is a 50% chance that paging will persistentlycollide with the reading of TC = 0. In this case, the priority of CBCHmay be raised to read the block at TC = 0. If the remaining three blocksalso need to be read, the priority of CBCH may again be raised. 3 1 Inthis case, paging read will not persistently collide with TC = 0.Therefore, it is not necessary to raise the priority of a CBCH read. Buta paging read will collide with one of the four message blocks. Althoughover two TC cycles it is possible to read all the CBCH blocks, it canlead to a garbled message. For this reason, it is advised to raise thepriority of a CBCH read. 4 1 This case is similar to the case of pagingcycle 2 in that one message block will persistently collide with theCBCH read. Therefore, the best approach is to raise the priority of CBCHreading over paging reading.

If a wireless communication device 104 does not have any knowledge ofwhat and when the network is broadcasting, the wireless communicationdevice 104 may have to read at least every cell broadcast channel (CBCH)block at TC=0. This equates to reading the cell broadcast channel (CBCH)at least once every 1.88 seconds (8*51*4.615 milliseconds (ms)=1.88seconds). Thus, a wireless communication device 104 may waste powerreading the cell broadcast channel (CBCH) block, only to discover thatthe wireless communication device 104 does not need this block.

To overcome this issue, the 3GPP specification has a mechanism wherebythe network sends a cell broadcast (CB) scheduling message on the cellbroadcast channel (CBCH). One cell broadcast (CB) message slot mayinclude TC=0, 1, 2 and 3 (or TC=4, 5, 6 and 7 for cell broadcast channel(CBCH) extended). A cell broadcast (CB) scheduling message may take upone message slot. The cell broadcast (CB) scheduling message maydescribe what is to be transmitted in upcoming message slots (up to 48upcoming message slots). The cell broadcast (CB) scheduling message mayalso describe to the wireless communication device 104 what will betransmitted in the upcoming cell broadcast (CB) message slots (e.g., anew message and its message ID 122, an old message and its message ID122 or no message).

Based on this information, the wireless communication device 104 maydetermine which message slots need to be read. The terms ‘old message’and ‘new message’ refer to whether what is being transmitted isdifferent than (new) or the same as (old) the previous cell broadcast(CB) scheduling message. Each cell broadcast (CB) scheduling message mayonly give information for up to 48 message slots. After this period, thewireless communication device 104 may either receive a new cellbroadcast (CB) scheduling message or, if the wireless communicationdevice 104 does not receive a new cell broadcast (CB) schedulingmessage, the wireless communication device 104 may start to read thecell broadcast channel (CBCH) every time TC=0 occurs.

However, real networks do not normally send cell broadcast (CB)scheduling messages. Thus, wireless communication devices 104 cannottake advantage of this feature. To overcome the deficiencies associatedwith a wireless communication device 104 reading the cell broadcastchannel (CBCH) at least every 1.88 seconds, the methods of FIG. 5 andFIG. 6 are introduced.

FIG. 5 is a flow diagram of a method 500 for optimizing the reception ofcell broadcast (CB) messages 436. The method 500 may be performed by awireless communication device 104. The method 500 may be performed bysingle-SIM wireless communication devices 104 and dual-SIM wirelesscommunication devices 104. Thus, the wireless communication device 104may have a first subscription and a second subscription. The wirelesscommunication device 104 may communicate 502 with a first cell using thefirst subscription. The wireless communication device 104 may thenswitch 504 to communicating with a second cell.

In the method 500 shown, the wireless communication device 104 may read506 the cell broadcast channel (CBCH) upon a cell change. Reading 506the cell broadcast channel (CBCH) may refer to searching for cellbroadcast (CB) messages 436 on the cell broadcast channel (CBCH). Thewireless communication device 104 may switch 508 from dedicated mode topacket (idle) mode. In embodiments of the present invention, thewireless communication device 104 may then reread 510 the cell broadcastchannel (CBCH) once. This way, the wireless communication device 104does not need to keep rereading the cell broadcast channel (CBCH) every1.88 seconds. The wireless communication device 104 may refresh the cellbroadcast (CB) message 436 every time the wireless communication device104 leaves dedicated mode after performing an action (e.g., a locationupdate, a voice call, etc.). The wireless communication device 104 doesnot need to reread the cell broadcast channel (CBCH) upon entering(packet) idle mode from packet transfer mode, as transitions betweenthese two states may happen frequently.

The method 500 may be suitable when cell broadcast (CB) messages 436 donot change very often. The customer may enable or disable this method500. However, the method 500 illustrated in FIG. 5 should be disabledautomatically if it is determined that a cell broadcast (CB) schedulingmessage is supported in the cell. Thus, upon cell selection orreselection, the wireless communication device 104 needs to determine ifcell broadcast (CB) scheduling message is supported in the cell. Thismay be accomplished by reading at least 49 consecutive message slots(which takes approximately 92 seconds (49*8*51*4.615=92)).

Furthermore, the method 500 of FIG. 5 has a drawback in that if thenetwork changes the cell broadcast (CB) message(s) 436, the wirelesscommunication device 104 will not detect this change until the wirelesscommunication device 104 either performs cell reselection or entersdedicated mode and then returns to packet (idle) mode.

FIG. 6 is a flow diagram of another method 600 for optimizing thereception of cell broadcast (CB) messages 436. The method 600 may beperformed by a wireless communication device 104. The method 600 may beperformed by single-SIM wireless communication devices 104 and dual-SIMwireless communication devices 104. The wireless communication device104 may receive 602 a trigger to read the cell broadcast channel (CBCH).One trigger to read the cell broadcast channel (CBCH) is the wirelesscommunication device 104 switching from one cell to another cell.Another trigger to read the cell broadcast channel (CBCH) is thewireless communication device 104 entering (packet) idle mode fromdedicated mode.

The wireless communication device 104 may determine 604 whether thenetwork supports cell broadcast (CB) scheduling message. As discussedabove in relation to FIG. 5, the wireless communication device 104 maydetermine 606 whether the network supports cell broadcast (CB)scheduling message by monitoring the cell broadcast channel (CBCH) for49 consecutive cell broadcast (CB) message slots (approximately 92seconds) after entering packet idle mode in a cell. If no cell broadcast(CB) scheduling message is received during this period, then thewireless communication device 104 assumes the network does not supportcell broadcast (CB) scheduling message.

If the network supports cell broadcast (CB) scheduling message, thewireless communication device 104 may reread 608 the cell broadcastchannel (CBCH) while taking into account the received cell broadcast(CB) scheduling information. The wireless communication device 104 maythen continue 614 reading the cell broadcast channel (CBCH) according toscheduling information.

If the network does not support cell broadcast (CB) scheduling message,the wireless communication device 104 may reduce 610 the rate at whichthe cell broadcast channel (CBCH) is read by using pseudo scheduling. Inother words, if the network does not support cell broadcast (CB)scheduling message, the wireless communication device 104 may read thecell broadcast channel (CBCH) at a lower rate than every 1.88 seconds.For example, the wireless communication device 104 may skip four messageslots after the last message slot read (and thus not read the cellbroadcast channel (CBCH) for approximately 10 seconds). The wirelesscommunication device 104 may then reread 612 the cell broadcast channel(CBCH) at the reduced rate. Rereading 612 the cell broadcast channel(CBCH) at the reduced rate may be referred to as pseudo scheduling.Pseudo scheduling is discussed in additional detail below in relation toFIG. 7 and FIG. 8. The wireless communication device 104 may thencontinue 614 reading the cell broadcast channel (CBCH) according toscheduling information.

One reason pseudo scheduling is able to be used is that cell broadcast(CB) messages 436 do not change very often. In general, each cellbroadcast (CB) message 436 does not change every 1.88 seconds. Also,there are no strict performance requirements for cell broadcast (CB)message 436 reception. Using pseudo scheduling may reduce powerconsumption in both single-SIM and dual-SIM wireless communicationdevices 104. It may also reduce the instances of cell broadcast channel(CBCH) read for one subscription colliding with paging channel (PCH)read of the other subscription. However, pseudo scheduling may fail toread a cell broadcast (CB) message 436, since pseudo scheduling uses anon-intelligent cell broadcast channel (CBCH) read rate.

In embodiments of the present invention, pseudo scheduling reuses thesame functionality in the wireless communication device 104 that isdesigned for real cell broadcast (CB) scheduling. The pseudo schedulingmechanism is flexible as it allows for different patterns for readingthe cell broadcast channel (CBCH). For dual-SIM cases, pseudo schedulingmay reduce the opportunity of collisions of page channel (PCH) readingon one subscription and cell broadcast channel (CBCH) reading on theother subscription.

The method 600 of FIG. 6 may have a lower standby time than the method500 of FIG. 5. The method 600 of FIG. 6 may also increase the powerconsumption of the wireless communication device 104 compared to themethod 500 of FIG. 5. However, the method 600 of FIG. 6 has theadvantage of the wireless communication device 104 being able to refreshthe cell broadcast (CB) messages 436 quicker than the method 500 of FIG.5. The method 600 of FIG. 6 may be enabled or disabled by the customer.The method 600 of FIG. 6 may be implemented by generating pseudoschedule information.

FIG. 7 illustrates data flows between a wireless communication device702 and a network 738, where pseudo scheduling is implemented afterdetermining that the network 738 has not sent a cell broadcast (CB)scheduling message. Upon receiving a cell broadcast channel (CBCH)description 740 from the network 738, a wireless communication device702 may start to monitor 742 the cell broadcast channel (CBCH) innon-DRX mode (i.e., the wireless communication device 702 starts to readevery radio block on the cell broadcast channel (CBCH) whenever TC=0).During this period (referred to as T_search_schedule 744 and controlledby a timer), the wireless communication device 702 is searching for thecell broadcast (CB) scheduling messages as well as for the desired cellbroadcast (CB) message(s) 436 from cell broadcast (CB) data (CB_BLOCK)746 a-b broadcast on the cell broadcast channel (CBCH).

Once the search for cell broadcast (CB) scheduling message is finished(i.e., after 49 consecutive cell broadcast (CB) message slots), if nocell broadcast (CB) scheduling message was received, the wirelesscommunication device 702 may generate 750 its own scheduling information(i.e., pseudo scheduling information) and start to read 752 the cellbroadcast channel (CBCH) according to this scheduling information. Thecell broadcast channel (CBCH) is given a higher priority than the pagingchannel (PCH).

In one configuration, the pseudo schedule information may be that ofTable 3 below.

TABLE 3  NM 1 = 0  NM 2 = 1  NM 3 = 0  NM 4 = 0  NM 5 = 0  NM 6 = 0  NM7 = 1  NM 8 = 0  NM 9 = 0 NM 10 = 0 NM 11 = 0 NM 12 = 1 NM 13 = 0 NM 14= 0 NM 15 = 0 NM 16 = 0 NM 17 = 1 NM 18 = 0 NM 19 = 0 NM 20 = 0 NM 21 =0 NM 22 = 1 NM 23 = 0 NM 24 = 0 NM 25 = 0 NM 26 = 0 NM 27 = 1 NM 28 = 0NM 29 = 0 NM 30 = 0 NM 31 = 0 NM 32 = 1 NM 33 = 0 NM 34 = 0 NM 35 = 0 NM36 = 0 NM 37 = 1 NM 38 = 0 NM 39 = 0 NM 40 = 0 NM 41 = 0 NM 42 = 1 NM 43= 0 NM 44 = 0 NM 45 = 0 NM 46 = 0 NM 47 = 1 NM 48 = 0

In the pseudo schedule information of Table 3, the wirelesscommunication device 702 may read every 5^(th) message (˜9.4 secondperiod) during a pseudo schedule period, thus reducing the rate for thecell broadcast channel (CBCH) read. Thus, the wireless communicationdevice 702 may read the NM 2 message, the NM 7 message, etc. Consecutiveschedules may shift the pseudo schedule period. This may give thewireless communication device 702 the opportunity to read other cellbroadcast (CB) message slots, in case multiple cell broadcast (CB)messages 436 broadcast cyclically.

FIG. 8 illustrates data flows between a wireless communication device802 and the network 838, where pseudo scheduling is renewedperiodically. The wireless communication device 802 may generate 854pseudo schedule information that reads every cell broadcast (CB) messageslot upon receiving a cell broadcast channel (CBCH) description 840 fromthe network 838. The wireless communication device 802 may then startmonitoring the cell broadcast channel (CBCH) according to this pseudoscheduling information.

During the schedule period, the wireless communication device 802 maysearch for a cell broadcast (CB) scheduling message from cell broadcast(CB) data (CB_BLOCK) 846 a-b broadcast on the cell broadcast channel(CBCH) from the network 838. If a cell broadcast (CB) scheduling messageis received from the network 838, the wireless communication device 802may implement the scheduling according to the cell broadcast (CB)scheduling message.

If the schedule period ends and no cell broadcast (CB) schedule messagewas received, the wireless communication device 802 may generate 856 newpseudo schedule information that does not require monitoring all cellbroadcast (CB) message slots. The wireless communication device 802 maythen start monitoring 858 the cell broadcast channel (CBCH) according tothe new pseudo scheduling information.

The wireless communication device may start to read the cell broadcastchannel (CBCH) in discontinuous reception (DRX) mode. The cell broadcastchannel (CBCH) may be given a higher priority than the paging channel(PCH).

FIG. 9 illustrates data flows on a wireless communication device 104that implements pseudo scheduling. In FIG. 9, an explicit timerT_search_schedule 944 is used on the wireless communication device 104.The wireless communication device 104 may include a wireless messagingservice (WMS) 951, a cell broadcast (CB) task 953, a GERAN radioresource (RR) layer 955 and a GERAN logical layer (L1) 957. The wirelessmessaging service (WMS) 951 may send a WMS search request (Message IDlist 960) to the cell broadcast (CB) task 953. The cell broadcast (CB)task 953 may then be initiated 961. The GERAN logical layer (L1) 957 maysend a PH DATA IND (SI4) 959 to the GERAN radio resource (RR) layer 955.The GERAN radio resource (RR) layer 955 may respond by sending aMPH_START_IDLEMODEREQ (CBCH description 965) to the GERAN logical layer(L1) 957. The GERAN radio resource (RR) layer 955 may also send a RRCELL CHANGE IND (CBCH present 967) to the cell broadcast (CB) task 953.

The wireless communication device 104 may then begin a search todetermine if cell broadcast (CB) scheduling is supported by the cell(referred to as T_search_schedule 944). The cell broadcast (CB) task 953may send a cell broadcast (CB) scheduling request 969 (CB_NON_DRX_MODE)to the GERAN logical layer (L1) 957. The GERAN logical layer (L1) 957may start to read 971 the cell broadcast channel (CBCH) in non-DRX mode.The cell broadcast channel (CBCH) may be given higher priority than thepaging channel (PCH). The GERAN logical layer (L1) 957 may then sendmultiple DL_CB_BLOCK_IND (cell broadcast (CB) data 973 a-b) to the cellbroadcast (CB) task 953. The DL_BC_BLOCK_IND may indicate the receptionof one block over the cell broadcast channel (CBCH). This block mayinclude an actual cell broadcast (CB) message 436, an empty block (i.e.,the network sent a filler frame) or a cell broadcast (CB) schedulingmessage.

Once the search for a cell broadcast (CB) scheduling message is finished(i.e., after 49 consecutive cell broadcast (CB) message slots), if nocell broadcast (CB) scheduling message was received, the cell broadcast(CB) task 953 may send a cell broadcast (CB) scheduling request 979(CB_DRX_MODE) to the GERAN logical layer (L1) 957. The GERAN logicallayer (L1) 957 may start to read 981 the cell broadcast channel (CBCH)in discontinuous reception (DRX) mode. The cell broadcast channel (CBCH)is given a higher priority than the paging channel (PCH). The cellbroadcast (CB) task 953 may then generate 977 pseudo scheduleinformation and read the cell broadcast channel (CBCH) according to thegenerated pseudo scheduling information.

If a cell broadcast (CB) schedule message is received during theT_search_schedule 944, the cell broadcast (CB) task 953 may configurethe GERAN logical layer (L1) 957 with the received cell broadcast (CB)schedule message.

FIG. 10 also illustrates data flows on a wireless communication device104 that implements pseudo scheduling. In FIG. 10, no explicit timer isused on the wireless communication device 104. The wirelesscommunication device 104 may include a wireless messaging service (WMS)1051, a cell broadcast (CB) task 1053, a GERAN radio resource (RR) layer1055 and a GERAN logical layer (L1) 1057. The wireless messaging service(WMS) 1051 may send a WMS search request (Message ID list 1059) to thecell broadcast (CB) task 1053. The cell broadcast (CB) task 1053 may beinitiated 1061. The GERAN logical layer (L1) 1057 may send a PH DATA IND(SI4 1063) to the GERAN radio resource (RR) layer 1055. The GERAN radioresource (RR) layer 1055 may respond by sending aMPH_START_IDLE_MODE_REQ (CBCH description 1065) to the GERAN logicallayer (L1) 1057. The GERAN radio resource (RR) layer 1055 may also senda RR CELL CHANGE IND (CBCH present 1067) to the cell broadcast (CB) task1053.

The cell broadcast (CB) task 1053 may generate 1068 pseudo scheduleinformation such that all cell broadcast (CB) message slots are to beread. The cell broadcast (CB) task 1053 may send a cell broadcastscheduling request (CB_DRX_MODE 1069) to the GERAN logical layer (L1)1057. The GERAN logical layer (L1) 1057 may start to read 1070 the cellbroadcast channel (CBCH) according to the pseudo schedule information.The GERAN logical layer (L1) 1057 may send multiple DL_CB_BLOCK_IND (CBdata 1075 a-b) to the cell broadcast (CB) task 1053 during the scheduleperiod indicating if a cell broadcast (CB) schedule message or a cellbroadcast (CB) message 436 is received.

If no cell broadcast (CB) schedule message was received and no cellbroadcast (CB) message 436 was received and the previous schedule periodexpires 1078 (i.e., the GERAN logical layer (L1) 1057 sends aCB_SCHED_EXPIRY_IND 1076 to the cell broadcast (CB) task 1053, the cellbroadcast (CB) task 1053 may generate 1080 new pseudo scheduleinformation with reduced frequency for cell broadcast channel (CBCH)read. The cell broadcast (CB) task 1053 may send a cell broadcast (CB)scheduling request (CB_DRX_MODE 1079) to the GERAN logical layer (L1)1057. The GERAN logical layer (L1) 1057 may then start to read 1081 thecell broadcast channel (CBCH) in discontinuous reception (DRX) mode. Thecell broadcast channel (CBCH) is given a higher priority than the pagingchannel (PCH).

FIG. 11 is a flow diagram of a method 1100 for receiving cell broadcast(CB) messages 436. The method 1100 may be performed by a wirelesscommunication device 104. The wireless communication device 104 may camp1102 on a cell. The wireless communication device 104 may detect 1104 acell broadcast channel (CBCH). The cell broadcast channel (CBCH) may bea downlink channel used to broadcast cell broadcast (CB) messages to allsubscribers within a cell. The wireless communication device 104 mayperform 1106 a cell broadcast (CB) continuous scan procedure inembodiments of the present invention. In one configuration, the wirelesscommunication device 104 may monitor the cell broadcast channel (CBCH)using the cell broadcast (CB) continuous scan procedure.

The wireless communication device 104 may then determine 1108 whethercell broadcast (CB) discontinuous reception (CB-DRX) is supported by thecell. If CB-DRX is supported by the cell, the wireless communicationdevice 104 may perform 1110 network CB-DRX procedures to receive cellbroadcast (CB) messages 436. If CB-DRX is not supported by the cell, thewireless communication device 104 may perform 1112 a predictive CB-DRXscan procedure to receive cell broadcast (CB) messages 436. The possibleoutcomes of the predictive CB-DRX scan procedure include a continuousscan being performed on every new message detection/failure of thepredictive CB-DRX scan procedure, a next predictive CB-DRX scanprocedure to wake up with the periodicity of each unique message or aCB-DRX mode if a schedule message is found.

FIG. 12 is a flow diagram of a method 1200 for receiving cell broadcast(CB) messages 436 using a cell broadcast (CB) continuous scan procedure.The method 1200 may be performed by a wireless communication device 104.The wireless communication device 104 may begin performing 1202 a cellbroadcast (CB) continuous scan procedure. The wireless communicationdevice 104 may start 1204 a continuous scan timer 118. The wirelesscommunication device 104 may read 1206 the cell broadcast channel (CBCH)every 1.88 seconds (every cell broadcast channel (CBCH) slot).

The wireless communication device 104 may determine 1208 whether themessage ID 122 and update number 129 have changed since the previouscell broadcast channel (CBCH) slot. If the message ID 122 or updatenumber 129 has changed since the previous cell broadcast channel (CBCH)slot, the wireless communication device 104 may restart 1204 thecontinuous scan timer 118. If the message ID 122 and update number 129have not changed since the previous cell broadcast channel (CBCH) slot,the wireless communication device 104 may increment 1210 the number ofrepetitions 120 for the message ID 122. The wireless communicationdevice 104 may determine 1212 whether the continuous scan timer 118 hasexpired. If the continuous scan timer 118 has not expired, the wirelesscommunication device 104 may return to reading 1206 the cell broadcastchannel (CBCH) every 1.88 seconds.

If the continuous scan timer 118 has expired, the wireless communicationdevice 104 may store 1214 the message ID 122, the cell ID 124, thenumber of repetitions 120, the last slot number 126 and the computedperiodicity 128 in memory. The wireless communication device 104 maystart 1216 a refresh timer 116. The wireless communication device 104may perform 1218 a predictive CB-DRX scan procedure. The wirelesscommunication device 104 may determine 1220 whether the refresh timer116 has expired. If the refresh timer 116 has not expired, the wirelesscommunication device 104 may continue to perform 1218 the predictiveCB-DRX scan procedure. If the refresh timer 116 has expired, thewireless communication device 104 may begin 1202 performing a cellbroadcast (CB) continuous scan procedure.

FIG. 13 is flow diagram of a method 1300 for performing a predictivecell broadcast discontinuous reception (CB-DRX) scan procedure. Themethod 1300 may be performed by a wireless communication device 104. Thewireless communication device 104 may begin 1302 performing a predictiveCB-DRX scan procedure. In embodiments of the present invention, thewireless communication device 104 may calculate 1304 cell broadcast (CB)message slots where desired cell broadcast (CB) messages 436 areexpected using the number of repetitions 120, the periodicity 128, andthe last slot number 126 of the last cell broadcast (CB) message 436. Asdiscussed above, the cell broadcast (CB) message slot in which a cellbroadcast (CB) message 436 is broadcast by a network does not usuallychange frequently. Thus, by observing when a desired cell broadcast (CB)message 436 is broadcast by a network, the wireless communication device104 may determine a cell broadcast (CB) message slot where a desiredcell broadcast (CB) message 436 is most likely to be broadcast.

The wireless communication device 104 may start 1306 a refresh timer116. The wireless communication device 104 may also start 1308 acontinuous scan timer 118. The refresh timer 116 may be used toperiodically move back to the cell broadcast (CB) continuous scanprocedure. The continuous scan timer 118 may be used to measure 49 cellbroadcast channel (CBCH) slots (which is a single cycle of predictiveDRX mode). The wireless communication device 104 may read 1310 the cellbroadcast channel (CBCH) only at the calculated slots.

The wireless communication device 104 may determine 1312 whether themessage ID 122 or update number 129 for the cell broadcast (CB) message436 has changed. If the message ID 122 or update number 129 has changedfor the cell broadcast (CB) message 436, the wireless communicationdevice 104 may perform 1314 a cell broadcast (CB) continuous scanprocedure. If the message ID 122 and update number 129 of the cellbroadcast (CB) message 436 have not changed, the wireless communicationdevice 104 may determine 1316 whether the continuous scan timer 118 hasexpired. If the continuous scan timer 118 has not expired, the wirelesscommunication device 104 may continue to read 1310 the cell broadcastchannel (CBCH) only at the calculated slots. If the continuous scantimer 118 has expired, the wireless communication device 104 maydetermine 1318 whether predictive scheduling has failed for any desiredmessage.

If predictive scheduling has failed for any desired message, thewireless communication device 104 may perform 1314 a cell broadcast (CB)continuous scan procedure. If predictive scheduling has not failed forany desired message, the wireless communication device 104 may determine1320 whether the refresh timer 116 has expired. If the refresh timer 116has expired, the wireless communication device 104 may perform 1314 acell broadcast (CB) continuous scan procedure. If the refresh timer 116has not expired, the wireless communication device 104 may start 1322the next cycle of the predictive CB-DRX scan procedure.

FIG. 14 illustrates certain components that may be included within awireless communication device 1402. The wireless communication device1402 may be an access terminal, a mobile station, a wirelesscommunication device, etc. In addition, the wireless communicationdevice can be, for example, wireless communication device 104 shown inFIG. 1.

In general, the wireless communication device 1402 can comprise a numberof components. The wireless communication device 1402 includes aprocessor 1403. The processor 1403 may be a general purpose single- ormulti-chip microprocessor (e.g., an ARM), a special purposemicroprocessor (e.g., a digital signal processor (DSP)), amicrocontroller, a programmable gate array, etc. The processor 1403 maybe referred to as a central processing unit (CPU). Although just asingle processor 1403 is shown in the wireless communication device 1402of FIG. 14, in an alternative configuration, a combination of processors(e.g., an ARM and digital signal processor (DSP)) could be used.

The wireless communication device 1402 also includes memory 1405. Thememory 1405 may be any electronic component capable of storingelectronic information. The memory 1405 may be embodied as random accessmemory (RAM), read-only memory (ROM), magnetic disk storage media,optical storage media, flash memory devices in RAM, on-board memoryincluded with the processor, EPROM memory, EEPROM memory, registers andso forth, including combinations thereof.

Data 1407 a and instructions 1409 a may be stored in the memory 1405.The instructions 1409 a may be executable by the processor 1403 toimplement the methods disclosed herein. Executing the instructions 1409a may involve the use of the data 1407 a that is stored in the memory1405. When the processor 1403 executes the instructions 1409 a, variousportions of the instructions 1409 b may be loaded onto the processor1403, and various pieces of data 1407 b may be loaded onto the processor1403.

The wireless communication device 1402 may also include a transmitter1411 and a receiver 1413 to allow transmission and reception of signalsto and from the wireless communication device 1402. The transmitter 1411and receiver 1413 may be collectively referred to as a transceiver 1415.An antenna 1417 may be electrically coupled to the transceiver 1415. Thewireless communication device 1402 may also include (not shown) multipletransmitters, multiple receivers, multiple transceivers and/or multipleantennas.

The wireless communication device 1402 may include a digital signalprocessor (DSP) 1421. The wireless communication device 1402 may alsoinclude a communications interface 1423. The communications interface1423 may allow a user to interact with the wireless communication device1402.

The various components of the wireless communication device 1402 may becoupled together by one or more buses, which may include a power bus, acontrol signal bus, a status signal bus, a data bus, etc. For the sakeof clarity, the various buses are illustrated in FIG. 14 as a bus system1419.

The techniques described herein may be used for various communicationsystems, including communication systems that are based on an orthogonalmultiplexing scheme. Examples of such communication systems includeOrthogonal Frequency Division Multiple Access (OFDMA) systems,Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems andso forth. An OFDMA system utilizes orthogonal frequency divisionmultiplexing (OFDM), which is a modulation technique that partitions theoverall system bandwidth into multiple orthogonal sub-carriers. Thesesub-carriers may also be called tones, bins, etc. With OFDM, eachsub-carrier may be independently modulated with data. An SC-FDMA systemmay utilize interleaved FDMA (IFDMA) to transmit on sub-carriers thatare distributed across the system bandwidth, localized FDMA (LFDMA) totransmit on a block of adjacent sub-carriers, or enhanced FDMA (EFDMA)to transmit on multiple blocks of adjacent sub-carriers. In general,modulation symbols are sent in the frequency domain with OFDM and in thetime domain with SC-FDMA.

The term “determining” encompasses a wide variety of actions and,therefore, “determining” can include calculating, computing, processing,deriving, investigating, looking up (e.g., looking up in a table, adatabase or another data structure), ascertaining and the like. Also,“determining” can include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” can include resolving, selecting, choosing, establishingand the like.

The phrase “based on” does not mean “based only on,” unless expresslyspecified otherwise. In other words, the phrase “based on” describesboth “based only on” and “based at least on.”

The term “processor” should be interpreted broadly to encompass ageneral purpose processor, a central processing unit (CPU), amicroprocessor, a digital signal processor (DSP), a controller, amicrocontroller, a state machine, and so forth. Under somecircumstances, a “processor” may refer to an application specificintegrated circuit (ASIC), a programmable logic device (PLD), a fieldprogrammable gate array (FPGA), etc. The term “processor” may refer to acombination of processing devices, e.g., a combination of a digitalsignal processor (DSP) and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with adigital signal processor (DSP) core, or any other such configuration.

The term “memory” should be interpreted broadly to encompass anyelectronic component capable of storing electronic information. The termmemory may refer to various types of processor-readable media such asrandom access memory (RAM), read-only memory (ROM), non-volatile randomaccess memory (NVRAM), programmable read-only memory (PROM), erasableprogrammable read-only memory (EPROM), electrically erasable PROM(EEPROM), flash memory, magnetic or optical data storage, registers,etc. Memory is said to be in electronic communication with a processorif the processor can read information from and/or write information tothe memory. Memory that is integral to a processor is in electroniccommunication with the processor.

The terms “instructions” and “code” should be interpreted broadly toinclude any type of computer-readable statement(s). For example, theterms “instructions” and “code” may refer to one or more programs,routines, sub-routines, functions, procedures, etc. “Instructions” and“code” may comprise a single computer-readable statement or manycomputer-readable statements.

The functions described herein may be implemented in software orfirmware being executed by hardware. The functions may be stored as oneor more instructions on a computer-readable medium. The terms“computer-readable medium” or “computer-program product” refers to anytangible storage medium that can be accessed by a computer or aprocessor. By way of example, and not limitation, a computer-readablemedium may include RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray® disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. It should be noted that acomputer-readable medium may be tangible and non-transitory. The term“computer-program product” refers to a computing device or processor incombination with code or instructions (e.g., a “program”) that may beexecuted, processed or computed by the computing device or processor. Asused herein, the term “code” may refer to software, instructions, codeor data that is/are executable by a computing device or processor.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isrequired for proper operation of the method that is being described, theorder and/or use of specific steps and/or actions may be modifiedwithout departing from the scope of the claims.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein, suchas those illustrated by FIGS. 5, 6, 11, 12 and 13, can be downloadedand/or otherwise obtained by a device. For example, a device may becoupled to a server to facilitate the transfer of means for performingthe methods described herein. Alternatively, various methods describedherein can be provided via a storage means (e.g., random access memory(RAM), read-only memory (ROM), a physical storage medium such as acompact disc (CD) or floppy disk, etc.), such that a device may obtainthe various methods upon coupling or providing the storage means to thedevice.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the systems, methods, and apparatus described herein withoutdeparting from the scope of the claims.

We claim:
 1. A method for receiving cell broadcast messages, comprising:communicating with a first cell; switching to communicating with asecond cell; reading a cell broadcast channel after switching cells;switching from a dedicated mode to a packet idle mode; and rereading thecell broadcast channel once after switching from a dedicated mode to apacket idle mode.
 2. The method of claim 1, wherein the method isperformed by a wireless communication device.
 3. The method of claim 2,wherein the wireless communication device uses one or more subscriberidentification module cards.
 4. The method of claim 1, wherein cellbroadcast scheduling message is not supported by the second cell.
 5. Themethod of claim 1, wherein reading a cell broadcast channel comprisessearching the cell broadcast channel for a cell broadcast message.
 6. Anapparatus for receiving cell broadcast messages, comprising: aprocessor; memory in electronic communication with the processor; andinstructions stored in the memory, the instructions being executable bythe processor to: communicate with a first cell; switch to communicatingwith a second cell; read a cell broadcast channel after switching cells;switch from a dedicated mode to a packet idle mode; and reread the cellbroadcast channel once after switching from a dedicated mode to a packetidle mode.
 7. The apparatus of claim 6, wherein the apparatus is awireless communication device.
 8. The apparatus of claim 7, wherein thewireless communication device uses one or more subscriber identificationmodule cards.
 9. The apparatus of claim 6, wherein cell broadcastscheduling message is not supported by the second cell.
 10. Theapparatus of claim 6, wherein reading a cell broadcast channel comprisessearching the cell broadcast channel for a cell broadcast message.
 11. Amethod for receiving cell broadcast messages, comprising: receiving atrigger to read a cell broadcast channel; determining that a networkdoes not support cell broadcast scheduling messages; reducing a rate atwhich the cell broadcast channel is read; and rereading the cellbroadcast channel at the reduced rate.
 12. The method of claim 11,wherein the method is performed by a wireless communication device. 13.The method of claim 12, wherein reducing the rate at which the cellbroadcast channel is read comprises using pseudo scheduling information.14. The method of claim 13, wherein the pseudo scheduling informationgives a cell broadcast channel higher priority than a paging channel.15. The method of claim 13, wherein the pseudo scheduling information issuch that the wireless communication device reads all cell broadcastmessage slots until a schedule map has expired.
 16. The method of claim11, further comprising: determining that all the desired messages havebeen read; and discontinuing rereading the cell broadcast channel at thereduced rate.
 17. An apparatus for receiving cell broadcast messages,comprising: a processor; memory in electronic communication with theprocessor; and instructions stored in the memory, the instructions beingexecutable by the processor to: receive a trigger to read a cellbroadcast channel; determine that a network does not support cellbroadcast scheduling messages; reduce a rate at which the cell broadcastchannel is read; and reread the cell broadcast channel at the reducedrate.
 18. The apparatus of claim 17, wherein the apparatus is a wirelesscommunication device.
 19. The apparatus of claim 18, wherein theinstructions executable to reduce the rate at which the cell broadcastchannel is read comprise instructions executable to use pseudoscheduling information.
 20. The apparatus of claim 19, wherein thepseudo scheduling information gives a cell broadcast channel higherpriority than a paging channel.
 21. The apparatus of claim 19, whereinthe pseudo scheduling information is such that the wirelesscommunication device reads all cell broadcast message slots until aschedule map has expired.
 22. The apparatus of claim 17, wherein theinstructions are further executable to: determine that all the desiredmessages have been read; and discontinue rereading the cell broadcastchannel at the reduced rate.
 23. An apparatus configured for receivingcell broadcast messages, comprising: means for communicating with afirst cell; means for switching to communicating with a second cell;means for reading a cell broadcast channel after switching cells; meansfor switching from a dedicated mode to a packet idle mode; and means forrereading the cell broadcast channel once after switching from adedicated mode to a packet idle mode.
 24. A computer-program product fora receiving cell broadcast messages, the computer-program productcomprising a non-transitory computer-readable medium having instructionsthereon, the instructions comprising: code for causing a wireless deviceto communicate with a first cell; code for causing the wireless deviceto switch to communicating with a second cell; code for causing thewireless device to read a cell broadcast channel after switching cells;code for causing the wireless device to switch from a dedicated mode toa packet idle mode; and code for causing the wireless device to rereadthe cell broadcast channel once after switching from a dedicated mode toa packet idle mode.